PROGRAM LANDER

      USE F2KCLI

      USE FTCL

CHARACTER(256) :: LINE
CHARACTER(256) :: EXE
CHARACTER(40)  :: CMD
INTEGER            :: NARG,IARG

NARG = COMMAND_ARGUMENT_COUNT()
WRITE(unit=*,fmt=*) "Arg count=", NARG

CALL GET_COMMAND(LINE)
WRITE(unit=*,fmt=*) "Line=",TRIM(LINE)
!
CALL GET_COMMAND_ARGUMENT(0,EXE)
WRITE(unit=*,fmt=*) "Program=",TRIM(EXE)
!

      CALL ftcl_start('/zvfs/config.tcl', EXE)

      ! Fetch constants defined in Tcl script
      CALL ftcl_get_int('impulse', impulse)
      CALL ftcl_get_real('ht', fheight)
      CALL ftcl_get_real('speed', speed)
      CALL ftcl_get_real('fuel', fuel)
      CALL ftcl_get_real('gross', gross)

      i = 0;
      

   DO WHILE (fheight .GT. 0)
        irdy = 0
        CALL ftcl_put_int('ready', irdy)
        CALL ftcl_script('wait4click')
        
        ! The Tcl burn variable now contains the amount of
        ! fuel to burn

        CALL ftcl_get_real('burn', burn)
        
        ! If we're out of fuel, no burn.
        IF (fuel .LE. 0)  THEN
          fuel = 0
          burn = 0
        CALL ftcl_put_real('burn', burn)
        ENDIF
        
        ! Calculate the speed
        CALL CALCSPEED (speed, fuel, gross, burn, impulse, speed)
        
        ! Update the local variables
        i = i + 1
        fuel = fuel - burn
        fheight = fheight - speed
        
        ! Update the Tcl variables
        CALL ftcl_put_int('time', i)
        CALL ftcl_put_real('speed', speed)
        CALL ftcl_put_real('fuel', fuel) 
        CALL ftcl_put_real('ht', fheight)
!        CALL ftcl_script('showState')
      ENDDO
      
      DO WHILE (1 .EQ. 1) 
 	CALL ftcl_script('update')
      ENDDO


      END

      SUBROUTINE CALCSPEED (finit, fuel, gross, burn, impulse, speed)
      mass = gross + fuel
      CALL ftcl_get_real('gravity', g)
      speed = speed + g - (impulse * log(mass/(mass-burn)))
      END